One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,5)(7,8)(9,10)(11,18)(12,16)(13,22)(14,17)(15,21)(19,24)(20,23)(25,26,30,34)(27,31,32,28)(29,33,37,40)(35,38,39,36)(9,11)(10,15)(12,19)(13,20)(14,21)(16,23)(17,18)(22,24)(25,27)(26,31)(28,34)(29,36)(30,32)(33,35)(37,38)(39,40) involution — undirected(2,5)(6,8)(9,12,14,13)(10,16,17,22)(11,19,21,20)(15,23,18,24)(25,28,34,27,30,31,26,32)(29,36,40,35,37,38,33,39)(9,13,14,12)(10,16,17,22)(11,20,21,19)(15,23,18,24)(29,37)(33,40)(35,39)(36,38)(1,3,4,7)(2,6,5,8)(11,21)(15,18)(19,20)(23,24)(25,29,26,33,30,37,34,40)(27,35,28,36,32,39,31,38)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.